Electroplating of Carbon Aerogels

By Naser Al-Mufachi

Reminder of Aerogels

Its appearance is similar to glass, however resembles solidified smoke.

Is a microporous, transparent silicate foam composed of ~99.8% air.

It is a stiff foam with a density ranging from 0.1-0.01 g/cm3. Is currently the worlds lowest density solid and hence the

worlds lightest solid. Can provide 39 times the insulation capabilities of the best

insulating fiberglass material. 1000 times less dense than glass. Was used on the Mars Path Finder Rover for insulation. Can support 500-4000 times its own weight in applied force. Has a high surface area (250-3000 m2/g).

….and of Carbon Aerogels

Electrically conductive Carbon nanofoams.

Available in forms of monoliths, granules, powders and papers.

The Carbon Aerogel has a high capacitance.

Commonly used as a high temperature insulator, coatings, electrodes fuel cells to name a few.

Properties of Carbon Aerogel

Available Ranges

Density 0.25–1.0 g/cm3

Surface Area 400 m2/g

Average Pore Size 0.7 nm

Electrical Resistivity

0.01-0.04 Ωcm

Capacitance 30 F/g

What the Carbon Aerogel should look like

What was observed

Carbon family

Carbon Aerogel

Carbon Graphite Rod

Carbon Felt

Recipe for Electrolyte Solutions

Solution Constituent Quantity of Constituent (g/L)

Nickel NiSO4·7H2O

NiCl2·6H2O

H3BO3

Wetting Agent (Isopropanol)

30050301

Iron Fe2SO4·7H2O

FeCl2·4H2O

(NH4)2SO4

NaCOOHH3BO3

Wetting Agent (Isopropanol)

300421515301

Chromium CrO3

H2SO4

4004

Initial Approach: Plating with Nickel

In order to get an idea of the electroplating process, a piece of copper sheet was plated with nickel. Adhesion of the Ni plate was excellent and the coating was uniform.

The idea would then be to move onto carbon articles which are similar to that of carbon aerogel.

Carbon Graphite was chosen for its conductive and brittle nature.

Carbon felt was selected for its porous features. Both of these were used to model the effects

and outcome of nickel plating Carbon Aerogels. Nickel was initially used for plating since it is the

easiest to electroplate with in general.

Plating Carbon Graphite

The Carbon graphite rods were prepared by wiping down the outer surface and cleaning with acetone.

The outcome revealed non-uniform plating.

Carbon is difficult to wet since it has a low surface energy.

A wetting agent was selected to help wet the graphite rod.

Different quantities were experimented with in order to decide which was the most effective in plating the rod.

Voltage (V) Current (mA) Time (sec) Observation

1 60 120 Blotchy plating i.e. very little

1.5 200 120, then further 180

One side plated thick, the other side plated non-uniformly

It was observed that at 2% isopropanol in nickel electrolyte solution yielded the best plating.

Conditions: 1.5V for 120 sec Current readings were increasing

during the plating session.

Vol. (%) Isopropanol (ml)

Observation

10 Very mild plating

8 Mild plating

6 Mild plating

4 Mild plating

2 Good plating

1 Mild plating

0.5 Very mild plating

Plating Carbon felt

2min at 3V in 2% isoprop. solution yielded mild plating on outer surface.

Another sample was done for 5min at 3V in 2% isoprop. Which showed much improved coverage.

This suggests that plating is time dependent.

However, the isopropanol is not ample enough to provide sufficient wetting.

Placing the sample in a vacuum chamber would help draw the air out of the pores and allow the electrolyte solution to infiltrate into the felt

Data collected for felt

The procedure involved attaching a strip of carbon felt to a copper rod.

The sample was then put in a 50ml beaker and sealed at the top using wax paper.

Holes were made to allow for air to pass out.

The sample was then evacuated for 30min runs, electroplated for 30 sec and massed after being further evacuated for 2hrs.

The results show a relative increase in mass however a dramatic drop in mass occurs at 150sec.

Could be put down to the electrolysing of water in the aqueous electrolyte.

Time elapsed (sec) Mass (g)

0 0.1886

30 0.1897

60 0.2060

90 0.3653

120 0.4078

150 0.2154

180 -

Time versus mass of Nickel deposition on Carbon felt

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0 50 100 150 200 250 300 350

Time (sec)

Mas

s o

f N

icke

l (g

)

Electroplating Set up

The sample was connected to the black chord which acts as the cathode electrode.

The red chord is attached to the metal desired for plating and plays the role of the anode.

The solution in the beaker is the electrolyte containing freely moving metal ions.

Plating is controlled using the voltage dial.

Preparation method

Samples are typically washed in distilled water and cleaned using acetone.

The samples were then fixed to a paperclip which was connected to a protruding copper wire and immersed in a batch of electrolyte.

The sample was then covered using wax paper and evacuated for 2hrs.

SEM Apparatus

The SEM and FESEM have been used to provide detailed images of the interior plating.

Unfortunately they have been unsuccessful in capturing any images which confirm metal plating.

EDS analysis has confirmed, at least, the presence of metal in the interior.

Nickel plated Carbon Aerogel

EDS Analysis

XRD Analysis

Nickel plate analysis

A Graph to show the mass deposition of Nickel on Carbon Aerogel (8/3/2005)

0.05

0.052

0.054

0.056

0.058

0.06

0.062

0.064

0.066

0 60 120 180 240 300

Time Elapsed (sec)

Mas

s D

epo

site

d (

g)

Iron plated Carbon Aerogel

EDS Analysis

A Graph to show the mass deposition of Iron on Carbon Aerogel (8/8/2005)

0.16

0.17

0.18

0.19

0.2

0.21

0 60 120 180 240 300

Time Elapsed (sec)

Mas

s D

epo

site

d (

g)

A large piece of aerogel broke off the original sample, hence the abrupt drop in mass.

In general

Massing the sample after successive plating sessions is a crude technique and yields no real useful data unfortunately.

The adhesion of the outer surface plating is poor and can peel off rendering the mass data inaccurate.

XRD scans are inconclusive and is a technique not suitable for analyzing on the scale being dealt with.

Only real evidence that plating occurs within the carbon aerogel is shown by the EDS scans.

Chromium plated Carbon Aerogel

In the making!All necessary data should be collected by

Monday.Research will continue.

Acknowledgement

Prof. Young BloodProf. TrumbleBen, Brad, John, Raghavan, Butur, DaveEntire Materials department.

Thank you for your time….Questions?